Optimization of the fractionated irradiation scheme considering physical doses to tumor and organ at risk based on dose–volume histograms

Ten patients with prostate cancer were each planned with 3 conventional and 3 conformal isocentric treatment techniques to compare the relative radiation doses to the bladder and rectal walls, and femoral head using dose volume histograms (DVH). The DVH were calculated for each organ and each technique, and the plans were ranked using the area under the curve method and also by the relative radiation dose given to specific normal tissue volumes.The results show that for the planning target volume chosen, the 4 field non-coplanar technique delivers the least dose to the bladder, the 6 field coplanar technique delivers the least dose to the rectum and the 3 field oblique technique delivers the least dose to the femoral heads. The 4-field technique with no shielding contributes the most dose to the bladder and rectum and the 6 field coplanar technique contributes the most dose to the femoral heads.No technique was shown to be optimal for all the organs at risk, but both the 6 field and 4 field non-coplanar field arrangements were shown to be superior techniques for minimising both the bladder and rectal dosage. The choice of technique will therefore depend on other factors such as the total prescribed dose, the ease of set-up and the ease of verification of isocentre reproducibility.

Download Full-text

Automated Robust Proton Planning Using Dose-Volume Histogram-Based Mimicking of the Photon Reference Dose and Reducing Organ at Risk Dose Optimization

International Journal of Radiation Oncology*Biology*Physics ◽

10.1016/j.ijrobp.2018.08.023 ◽

2019 ◽

Vol 103 (1) ◽

pp. 251-258 ◽

Cited By ~ 4

Author(s):

Roel G.J. Kierkels ◽

Albin Fredriksson ◽

Stefan Both ◽

Johannes A. Langendijk ◽

Daniel Scandurra ◽

...

Keyword(s):

At Risk ◽

Dose Optimization ◽

Dose Volume Histogram ◽

Reference Dose ◽

Dose Volume ◽

Organ At Risk

Download Full-text

Evaluation of plan optimisers in prostate VMAT using the dose distribution index

Journal of Radiotherapy in Practice ◽

10.1017/s1460396919000098 ◽

2019 ◽

Vol 18 (4) ◽

pp. 323-328 ◽

Cited By ~ 1

Author(s):

James C. L. Chow ◽

Runqing Jiang ◽

Lu Xu

Keyword(s):

At Risk ◽

Dose Distribution ◽

Organs At Risk ◽

Volumetric Modulated Arc Therapy ◽

Target Volume ◽

Weighting Factor ◽

Target Coverage ◽

Dose Volume Histograms ◽

Dose Volume ◽

Distribution Index

AbstractPurpose:Dose distribution index (DDI) is a treatment planning evaluation parameter, reflecting dosimetric information of target coverage that can help to spare organs at risk (OARs) and remaining volume at risk (RVR). The index has been used to evaluate and compare prostate volumetric modulated arc therapy (VMAT) plans using two different plan optimisers, namely photon optimisation (PO) and its predecessor, progressive resolution optimisation (PRO).Materials and methods:Twenty prostate VMAT treatment plans were created using the PO and PRO in this retrospective study. The 6 MV photon beams and a dose prescription of 78 Gy/39 fractions were used in plans with the same dose–volume criteria for plan optimisation. Dose–volume histograms (DVHs) of the planning target volume (PTV), as well as of OARs such as the rectum, bladder, left and right femur were determined in each plan. DDIs were calculated and compared for plans created by the PO and PRO based on DVHs of the PTV and all OARs.Results:The mean DDI values were 0·784 and 0·810 for prostate VMAT plans created by the PO and PRO, respectively. It was found that the DDI of the PRO plan was about 3·3% larger than the PO plan, which means that the dose distribution of the target coverage and sparing of OARs in the PRO plan was slightly better. Changing the weighting factors in different OARs would vary the DDI value by ∼7%. However, for plan comparison based on the same set of dose–volume criteria, the effect of weighting factor can be neglected because they were the same in the PO and PRO.Conclusions:Based on the very similar DDI values calculated from the PO and PRO plans, with the DDI value in the PRO plan slightly larger than that of the PO, it may be concluded that the PRO can create a prostate VMAT plan with slightly better dose distribution regarding the target coverage and sparing of OARs. Moreover, we found that the DDI is a simple and comprehensive dose–volume parameter for plan evaluation considering the target, OARs and RVR.

Download Full-text